Brush mechanism for dynamo-electric machines



1366- 1932- F. CARLSTEDT BRUSH MECHANISM FOR DYNAMO ELECTRIC MACHINES OrigEnal Filed Dec. 24. 1950 w: 75;, ATTo' NEY mutator.

Patented Dec. 20, 1932 UNITED STATES PATENT OFFICE FREDRIK CARLSTEDT, OF STOCKHOLM, SWEDEN, ASSIGNOR, BY MESNE ASSIGNMENTS, TO ELECTROLUX CORPORATION, A CORPORATION 01 DELAWARE BRUSH MECHANISM FOR DYNAMO-ELECTRTC MACHINES Continuation of application Serial No. 504,440, filed December 24, 1930, and in Germany December 28,

1929. This application filed January 5, 1931.

This application is filed to replace my copending application Serial No. 504,440, filed in the United States on December 24th, 1930, for which a corresponding application was filed in Germany on December 28th, 1929. This application is to be considered as relating back to the filing date of application Serial No. 504,440 herein continued and to the rights incident thereto.

My invention relates to dynamo-electric machines and more particularly to the commutator and brush mechanism for distributing or collecting the electric current.

The brush or brushes of a dynamo-electric machine are usually urged toward the commutator by a spring. The brushes are usually made of carbon. These brushes wear by contact with the commutator. Such brushes are sometimes carried in metal holders. Unless provision is made to the contrary, there is a danger that the metallic holder or the spring will come into contact with the commutator when the brush has been worn as far as the holder or spring. Such contact, if permitted, will destroy the commutator and necessitate rebuilding of the machine.

One of the objects of my invention is to provide apparatus for entirely removing the brush from the commutator when it has been substantially worn and to do this without having any other part contact the com- When the brush is removed from the commutator, there must be a force to accomplish this and I do not wish this force to react against the commutator, because, even if the reaction is taken up against the commutator by an insulating surface, there is likely to be injury to the commutator on account of failure of the reacting member. A further object of the invention is to provide apparatus for removing the brush from the commutator While preventing spring contact with the commutator by abutment of such spring against a fixed part. A further object of the invention is to provide. such mechanism for a longitudinally removable brush directed towards the side surface of a commutator. A still further object of the invention is to cause the removal of the Serial No. 506,635.

brush without leaving any parts likely to arc.

The above and other objects of the invention and the nature thereof will be apparent from the following specification taken in conjunction with the accompanying drawing showing several embodiments of the invent1on, which drawing forms a part of this specification.

Referring to the drawing:

Fig. 1 shows a dynamo-electric machine to which the invention is applied;

Fig. 2 is a longitudinal section through a brush guide and associated parts constructed in accordance with the invention;

Fig; 3 is a transverse section taken on the line 33 of Fig. 2;

Fig. 4 is a side view, partly cut away, of the brush holding apparatus;

Fig. 5 illustrates the removal of the brush from the commutator when it has been substantially worn;

Fig. 6 shows the brush holding apparatus with the brush removed;

Fig. 7 shows the brush per se;

Fig. 8 shows another embodiment of the invention with the parts in position before the brush has been worn away;

Fig. 9 shows the embodiment of Fig. 8 with the brush removed;

Fig. 10 is a view similar to Fig. 2 of still another embodiment of the invention;

Fig. 11 is a sectional view taken on the line 11-11 of Fig. 10; and

Figs. 12, 13 and 14 are views similar to Figs. 4, 5 and 6 of the embodiment shown in Fig.10.

The dynamo-electric machine is indicated generally by the reference character 10. The machine includes the commutator 11. The motor housing includes two brush holding members 12. These members 12 are made of insulating material and are secured to the motor housing by means of screws 13. Each member ,12, as shown more clearly in Fig. 2, has a longitudinal circular passa e into which is screwed a brush guide 14. rush guide 14 is of generally cylindrical outer surface and has an inner substantially rectangular bore 9 (see Fig. 3). The sides of the rectangular bore 9 are cut away as shown in Fig.

3 so that a circular member can fit into the bore as will presently be explained. Brush guide 14 is made of conducting material such as metal. The electric lead may be and is preferably connected to brush uide 14.

Guide 14 serves as a guide or the carbon brush 15 which is of generally rectangular cross-section to fit the bore 9. The two lateral dimensions of the brush are shown in Figs. 2 and 4 respectively. A cap 16 is screwed onto the outer end of guide 14. This cap is made of insulating material. A relatively long spiral spring is situated within bore 9 and acts between the cap 16 and one end of brush 15. In order to facilitate placing spring 17 in the bore, a shell 18 may be provided surrounding the spring. Shell 18 has an enlargement at the outer end which is held between cap 16 and the outer end of uide 14. Shell 18 is circular as shown in Fig. 3 and it is to accommodate this member that the sides of the rectangular bore are cut away as shown.

The carbon brush 15 is provided with a slot 20 at the end opposite the commutator. This slot extends transversely to the wider lateral sides of the carbon brush. The slot has curved side surfaces to receive curved portions 22, which may be termed tongs, of a pincer-like spring 21. Spring 21 has an unstressed position with the tongs 22 separated as shown in Fig. 5. This spring is compressed in order that the tongs 22 may fit into slot 20 and, in the position shown in Fig. 2, the spring exerts equal and opposite lateral forces on the side surfaces of the slot tending to separate the projecting parts 26 of the brush which are formed by and to the sides of the slot.

A current conducting wire 24 is soldered to the end of shell 18 and to the hinge end of spring 21. The length of this wire 24 is preferably such that the spring 21 can move toward the commutator a given distance but is limited in movement beyond such given distance. Two openings 27 are provided in the sides of guide 14 adjacent the commutator. These openings 27 are diametrically opposed and on the narrower lateral sides of the brush and are wider than this width of the brush. These openings are cut into the guide from the commutator end.

An abutment 28 projects from guide 14 into the bore 9. This abutment may be, as shown, in the form of an adjustable screw. The extent of projection of the abutment is such as to be radially inward beyond the edge of spring 17 but not so far as to contact the carbon brush.

The above described arrangement operates as follows: With the parts in position as shown in Fig. 2, spring 17 urges the brush toward the commutator. It will be seen that the bore 9 is at right angles to the axis of the commutator and is in alignment with the contact surface of the commutator. As the end surface of the brush wears by contact with the commutator, the remainder of the brush moves toward the commutator. This continues with the parts in the relation shown in Fi 2, spring 17 extending, wire 24 approac ing tautness and spring 21 approaching the commutator. The current is carried through guide 14, shell 18, wire 24 and the.

brush (except as far as there may be direct transmission of current between the brush and guide 14) The two projecting parts 26 of the carbon brush separated by the slot 20 are held together by the main body of the brush. When the brush has been substantially worn so that the body portion is practically gone, there will not be suflicient cohesion in what is left in the main body portion to hold the projecting parts together against the lateral pressure of spring 21. Thus, when the tongs 22 are opposite slots 27 and the brush has worn substantially to the bottom of slot 20, the tension in spring 21 overcomes the cohesion of the carbon and breaks the remainder of the brush apart, throwing the separated parts through the openings 27 as illustrated in Fig. 5. Thus the carbon brush is entirely removed from the commutator when it is substantially worn.

When this separation of the brush from the commutator occurs, spring 17 is prevented from reaching the commutator by contacting abutment 28. Spring 21 is prevented from moving toward the commutator because the wire 24 is made of such length that the spring 21 cannot approach the commutator to a greater degree than is shown in Fig. 5.

Fig. 4 shows the position of the parts just before the brush is removed from the commutator. 'Fig. 5 shows the removal and Fig. 6 shows the position after removal of the brush. It will be obvious that when the brush is removed the circuit of the machine is opened and the machine will stop if it is a motor and cease to deliver current if it is a generator. It will be seen from Figs. 5 and 6 that when this removal of the brush takes place, there is no part whatsoever in contact with the commutator and no part which is likely to touch the commutator on any account.

Figs. 8 and 9 show another embodiment of the invention in which the removal of the brush takes place by having the remainder of the brush after separation pulled back by collapse of the pincer-like spring. In this embodiment the end of the carbon brush opposite to the commutator is provided with two diagonal slots or notches 29 and 30 which form a head 32 having tapering surfaces. The pincer-like spring, which in this case, designated by numeral 31, is stressed oppositely to the previously described spring 21 and the tongs thereof tend to move together. These tongs contact the aforesaid tapered portion of the head. -As in the previous cmbodiment, the pincer-like spring is connected, as by soldering, to the lead wire 24. The slots 29 and 30 also form projections 33 and 34 which cooperate with the tongs of the pincer-like spring to prevent the approach of the tongs toward each other so long as the parts of the brush are not separated. Spring 17 in this case abuts a ainst shoulders formed in spring 31 to urge t e carbon brush toward the commutator.

, In the operation of this embodiment, when the brush has Worn substantially as far as the slots 29 and 30,'head 32 becomes separated under the action of spring 31, which may be aided by spring 17. The shoulders 33 and 34 are thrown through openings 27 or they will fall away from the commutator and the head 32 is pulled back from the commutator to the position shown in Fig. 9 due to collapse of spring 31. In this arrangement, also, the Wire 24 is used to limit the movement of spring 31 toward the commutator. This wire, in this case, also serves to prevent spring 17 from contacting the communtator. The shoulders of the spring 31 against which spring 17 acts may be said to be the abutment in this case, which abutment is limited as to movement toward the commutator by the wire 24. Obviously the arrangement in Figs. 8 and 9 may be such that the spring 17 slips over spring 31 in which case an abutment such as 28 is necessary.

In each of the embodiments above described, the wire 24 is relied on to prevent one or both of the springs from reaching the commutator. It is conceivable that the soldering of this wire may not hold and I have therefore devised an arrangement wherein this wire is not depended upon to prevent contact of the respective parts with the commutator This embodiment is shown in Figs. 10 through 14. In this embodiment a spring 35 is providedbetween loops or abutments 36 of the arms of spring 21 and the end of the bgush. This spring 35 is stifi'er than spring 1 1 In this embodiment, spring 35 has no function until the lu'ushis worn to the breakin point; brush and the abutments 36, the last turn of the coil being held in the bends 36. When the brush is substantially worn and the parts 26 are separated, spring 35 expands. But before this spring has had time to expand, spring 21 has expanded and spring 36 therefore abuts against the tongs 22 as shown in Fig. 13. The abutment 28 is provided against which spring 35 abuts. The spring 35 being stifi'er than spring 17 then pushes springs 17 and 21 backwards preventing them from contacting the commutator.

While I have shown some embodiments of the invention, it will be understood that many other embodiments are possible and that the tact surface, a brush in said guide, means to.

urge said brush against said commutator and means to automtically remove the brush from contact with the commutator when the brush is substantially worn.

2. In a dynamo-electric machine, a commutator, a brush guide having a longitudinal bore in alignment with the commutator contact surface, a brush-in said guide, means to urge said brush against said commutator and means to automatically remove the brush from contact with the commutator when the brush is substantially Worn without exerting force against the commutator.

3. In a dynamo-electric machine, a commutator, a brush guide having a longitudinal bore in alignment with the commutator contact surface and having openings adjacent the commutator, a brush in said guide, means to urge said brush against said commutator and means to automatically remove the brush from contact with the commutator through said openings When the brush is substantially worn.

4. In a dynamo-electric machine, a commutator, a brush guide having a longitudinal bore in alignment with the commutator contact surface and having opposed openings adj acent the commutator, a brush in said guide, means to urge said brush against said commutator and means to remove the brush from contact with the commutator when the brush is substantially worn by dividing the brush into parts and ejecting the parts through said openings.

5. In a dynamo-electric machine, a commutator, a brush guide having a longitudinal bore in alignment with the commutator contact surface, a brush in said guide, means to urge said brush against said commutator, and means to remove the brush from contact with g the commutator when the brush is substantial- It is clamped betweenthe end of the 1 y worn, comprising a spring exerting equal and opposite forces laterally on the brush.

6. In a dynamo-electric machine, a commutator, a brush guide having a longitudinal bore in alignment with the commutator contact surface, a brush in said guide having a slotted portion, means to urge saidbrush against said commutator, and means to remove the brush from contact with the commutator when the brush is substantially worn comprising a spring cooperating with said slotted portion and exerting equal and opposite forces laterally on the brush.

7. In a dynamo-electric machine, a commutator, a brush guide having a longitudinal bore in alignment with the commutator con-.

tact surface, a brush in said guide having a tapered head, means to urge said brush against said commutator, and means to re move the brush from contact with the commutator when the brush is substantially worn comprising a spring cooperatin with said tapered head and exerting equal and opposite forces laterally on the brush.

8. In a dynamo-electric machine, a commutator, a brush guide having a longitudinal ,bore in alignment with the commutator contact surface and having openings adjacent the commutator, a brush in said guide having a slotted portion, means to urge said brush against said commutator, and means to remove the brush from contact with the commutator when the brush is substantially worn comprising a spring exerting equal and opposite forces laterally on the brush and acting to eject parts of the brush through said openings.

9. In a dynamo-electric machine, a commutator, a brush guide having a longitudinal bore in alignment with the commutator contact surface, a brush in said guide, a spring in said bore for urging said brush against said commutator, means to automatically remove the brush from contact with the commutator when the brush is substantially worn and means to limit the movement of said spring toward the commutator.

10. In a dynamo-electric machine, a commutator, a brush guide having a longitudinal bore in alignment with the commutator contact surface, a brush in said guide, a spring in said bore for urging said brush againstsaid commutator, means to automatically reremoy e the brush from contact with the commutator when the brush is substantially worn and an abutment projecting outwardly from .said guide to limit the movement of said spring toward the commutator.

11. In a dynamo-electric machine, a commutator, a brush guide having a longitudinal bore in alignment with the commutator contact surface, a brush in said guide, a spring in said bore for urging said brush against said commutator, a spring to remove the brush from contact with the commutator when the brush is substantially worn and means to limit the movement of both said springs toward the commutator.

12. In a dynamo-electric machine, a commuator, a brush guide having a longitudinal bore in alignment with the commutator contact surface, a brush in said guide, a spring in said bore for urging said brush a ainst said commutator, meansto remove the rush from contact with the commutator when the brush is substantially worn and means to move said spring away from the commutator when said brush is removed.

13. In a dynamo-electric machine, a commutator, a brush guide having a longitudinal bore in alignment with the commutator contact surface, a brush in said guide, a spring in said bore for urging said brush against said commutator, a spring to remove the brush from contact with the commutator when the brush is substantially worn and means to move both said s rings away from the commutator when the rush is removed.

14.. In a dynamo-electric machine, a commutator, a brush guide having a longitudinal bore in alignment with the commutator contact surface, a brush in said guide, a spring in said bore for urging said brush against said commutator, means comprising a lateral pressure spring to remove the brush from contact with the commutator when the brush is substantially worn, an abutment projecting from said guide to limit the movement of said first mentioned spring toward the commutator, and means comprisin a conductor wire for limiting movement 0 said secondmentioned spring toward the commutator.

In testimony whereof I have aflixed my signature.

FREDRIK CARLSTEDT. 

